1. Field of the Invention
This invention relates to a light guide member for guiding light emitted by a stimulable phosphor sheet to a photodetector during the image read-out step in a radiation image recording and reproducing system wherein the stimulable phosphor sheet is exposed to a radiation passing through an object to have a radiation image stored therein, the stimulable phosphor sheet carrying the radiation image stored therein is scanned by stimulating rays which cause it to emit light in proportion to the radiation energy stored, the emitted light is photoelectrically detected and converted to an electric image signal, and a visible image is reproduced by use of the electric image signal.
2. Description of the Prior Art
The radiation image recording and reproducing system as described above is disclosed, for example, in U.S. Pat. Nos. 4,258,264 and 4,315,318, and Japanese Unexamined Patent Publication No. 56(1981)-11395. The radiation image recording and reproducing system was also described in "Nikkan Kogyo Shinbun" (Daily Industrial Newspaper), June 23, 1981 edition, page 16. The light guide member used for image read-out in the radiation image recording and reproducing system is disclosed, for example, in U.S. Pat. No. 4,346,295.
In order to improve the light guiding efficiency of the light guide member and to realize efficient image read-out with a small apparatus, the applicant proposed a novel light guide member provided with a dichroic optical plane in Japanese patent application No. 58(1983)-218678. However, a need exists for a light guide member further improved in design. FIGS. 1 and 2 are sectional side views showing embodiments of the light guide member described in Japanese patent application No. 58(1983)-218678, and FIG. 3 is an enlarged view of FIG. 1. In the embodiments of FIGS. 1 and 2, stimulating rays entering the light guide member in the direction as indicated by the arrow A cause the stimulable phosphor sheet to emit light in the directions as indicated by the arrows B1, B2 and C. The light emitted in the directions as indicated by the arrows B1 and B2 are reflected efficiently and guided inside of the light guide member. However, the light emitted in the direction as indicated by the arrow C comes out of the upper surface of a block 1. The light guide member as shown in FIG. 1 is advantageous over the light guide member as shown in FIG. 2 in that a photodetector such as a photomultiplier can be easily connected to the end portion of the block 1. On the other hand, the latter is advantageous over the former in that the height of the apparatus can be made small and the size of the whole apparatus can be decreased.
Further, as shown in FIG. 3, the embodiment of FIG. 1 is disadvantageous in that some components of the light emitted by the stimulable phosphor sheet come out of the light guide member as indicated by the arrows D and E. Thus it is desired to further improve the light guiding efficiency.